Specific reading disability (dyslexia) is a heterogenous disorder, but there is evidence that in some cases it is genetically determined and may be dominantly inherited. This study utilizes linkage analysis to investigate this possibility, the assumption being that a significant lod score between reading disability and a known gene is best explained by the presence of a major gene for dyslexia. In addition, the neuropsychological characteristics of familial dyslexia are investigated using a battery of tests suggested by the work of Mattis et al. (1975) and Boder (1973). The Mattis study defined 3 different subtypes of dyslexia based on neuropsychological characteristics, while Boder utilized analysis of spelling errors to characterize 3 types of dyslexics. If either of these classification systems are detecting different mechanisms for dyslexia, the following hypotheses should hold: 1) Within a family, affected members should be classified into the same subgroup; and 2) Affected individuals from families showing the same linkage relationship should be classified into the same subgroup. Alternatively, familial dyslexia may form a unique subgroup not fitting any previous catagorization, and the pattern of results on the test battery should reflect this. Identification of a genetic basis for dyslexia and description of the phenotype would not only facilitate recognition and appropriate remediation for affected children and early detection of children at high risk, but would open up research into genetic influences on reading and other cognitive abilities.